Fracturing Behavior Study of Three-Flawed Specimens by Uniaxial Compression and 3D Digital Image Correlation: Sensitivity to Brittleness

Brittleness has significant effects on the fracturing behaviors of preflawed rock-like materials. In this study, uniaxial compressive experiments are conducted on rock-like specimens containing three flaws, and a three-dimensional digital image correlation technique is applied to capture the real-time displacement and strain fields on the rock-like specimens' surface. The present experimental study focuses on the effects of the brittleness of rock-like materials on crack initiation, propagation, and coalescence behaviors in three flaw-contained specimens. The experimental results show that the crack initiation mode transforms from the tensile mode to the shear mode with a decrease in the brittleness index of rock-like materials. Meanwhile, crack coalescence modes transform from the tensile crack coalescence mode to the mixed tension-shear coalescence mode, then to the shear coalescence mode as the brittleness index of rock-like materials decreases. Moreover, the ratio of the crack initiation stress to the peak stress increases, while the ratio of the crack coalescence stress to the peak stress decreases as the brittleness index decreases. This paper also addresses the influences of the rock bridge angle on the mechanical and cracking behaviors of three flaw-contained specimens. For specimens with the lower brittleness index, the ratio of the crack initiation stress to the peak stress decreases, while the ratio of the crack coalescence stress to the peak stress increases as the rock bridge angle increases. However, for specimens with the higher brittleness index, the ratio of the crack initiation stress to the peak stress and the ratio of the crack coalescence stress to the peak stress decrease with increasing the rock bridge angle. The experimental results provide a better understanding of the sensitivity of mechanical and cracking behaviors of three flaw-contained specimens to the brittleness of rock-like materials under uniaxial compression.